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I am new to C and I am currently dealing with array functions.

There is my problem, I am asking user to input his username, and I would like to allow number, char, and space as first character. So I created a function to prevent user from just typing spaces using a do-while loop. At the first iteration, if I only 4 spaces type the 'filter' works perfectly, but if I type 4 spaces again, the function considerer thoses spaces as good. Here is the code:

void user_name (char *name) {
    int nb_space = 0;
    char buffer;
    do {
        printf("Player, please type your username \n");
        memset(name,'\0', sizeof(*name));
        scanf("%99[^\n]", name);// Using REGEX to prevent buffer issues with '\n'
        for(int i=0;i< sizeof(name);i++){
            if (name[i] == (char) ' '){
                nb_space++;
            }
        }
        while ((buffer = (char) getchar()) != '\n' ? buffer != EOF : false);//Using 'getchar' to empty the buffer 
    } while (nb_space == strlen(name));//I tryed to replace strlen with sizeof but nothing have changed
    first_maj(name);
}

And there is the caller:

int main(int argc, char** argv){
    char name[100];
    user_name(name);
    printf("your name: %s\n",name);//to check what we got 
}

The "first_maj" function is just a fonction which capitalizes the first char of each separated word. This is the output I got (I represente the spaces with '.':

Player, please type your username
....
Player, please type your username
....
your name: ....

The program should asks again and again until the user types a character after the 4 spaces, or simply types directly characters. Exemple of wished output (dots = spaces): 

Player, please type your username
.....
Player, please type your username
...john.rambo
your name: ...John.Rambo

Where is my mistake ? I could not figure out what is wrong in this code.

EDIT #1

Here is the capitalize function "first_maj" if it is important to find my mistake:

void first_maj (char name[]){
    if (isalpha(name[0])){
        name[0]= (char) toupper(name[0]);
    }
    for(int i=1;i<strlen(name);i++){
        if (isalpha(name[i]) && name[i-1] == ' '){
            name[i] = (char) toupper(name[i]);
        }
    }
}

EDIT #2

My question was about the iteration issue, not exactly the size of the array, but thank to you i could realize about other mistake. After reviewing the code with the debug function, i finally found the mistake I was looking for: I just forgot to reinitialize nb_space within the loop:

void user_name (char *name, int length) {
        int nb_space;
        char buffer;
        do {
            nb_space = 0;
            printf("Player, please type your username \n");
            memset(name,'\0', sizeof(*name));
            scanf("%99[^\n]", name);// Using REGEX to prevent buffer issues with '\n'
            for(int i=0;i< sizeof(name);i++){
                if (name[i] == (char) ' '){
                    nb_space++;
                }
            }
            while ((buffer = (char) getchar()) != '\n' ? buffer != EOF : false);//Using 'getchar' to empty the buffer 
        } while (nb_space == strlen(name));//I tryed to replace strlen with sizeof but nothing have changed
        first_maj(name);
    }
Maxime Deletraz
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  • 6
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    How to create a Minimal, Complete, and Verifiable example http://stackoverflow.com/help/mcve – NeoR Dec 22 '16 at 19:26
  • 3
    `sizeof(*name)` is wrong, and so is `sizeof(name)`. – n. m. could be an AI Dec 22 '16 at 19:28
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    Neither `sizeof(*name));` nor `sizeof(name));` is of any use in a function which is passed a pointer, because the only information you have, is a pointer, and its type. – Weather Vane Dec 22 '16 at 19:29
  • You need to have an size_t or int parameter in both the user_name() and first_maj() functions. Because those functions are getting only a pointer to a buffer of chars, they have no way of knowing the size of the buffer. You must pass the length in. So to call user_name: `user_name(name,100)` and the prototype should be `void user_name( char *, int length)` – Chimera Dec 22 '16 at 19:44
  • @Chimera: "*You need to have an size_t or int parameter in both the user_name() and first_maj() ...*" Why to `first_maj()`? – alk Dec 22 '16 at 19:48
  • @alk Because first_maj() is being passed a pointer to an array. The length isn't known. Look how it's being called from user_name(). – Chimera Dec 22 '16 at 19:52
  • @alk Granted, first_maj() isn't well written and *shouldn't* need to know the length because the passed in array is NULL terminated. But my comment speaks to the actual implementation of first_maj(). – Chimera Dec 22 '16 at 20:20

0 Answers0